Sound reproducer



June 11, 1929. L, cRoucH SOUND REPRODUCER Filed Feb 16, 1927 fly JAMESL. CROUCH Patented June 11, 1929.

UNITED STATES PATENT OFFICE.

JAMES L. CROUCH, OF SUMMIT, NEW JERSEY, ASSIGNOR TO BELL TELEPHONE LAB-ORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

SOUND BEPRODUCER.

Application filed February 16, 1927. Serial No. 168,787.

This invention relates to sound reproducers employing large directacting diaphragms.

An object of the invention is to reproduce efiicicntly and faithfullyall sounds Within the audible range.-

One feature of the invention resides in constructing a diaphragm of aplurality of sections of thin material arranged in a plane with theiradjacent edges slightly out of con tact.

Another feature of the invention relates to the use of bridging membersin a diaphragm of the foregoing type for connecting the various sectionstogether thereby causing substantially the entire surface of thediaphragm to vibrate as a Whole for the lower frequencies.

Another feature resides in rigidly mounting the bounding edge of adiaphragm made up as aforementioned.

The invention may be more readily understood by reference to thefollowing detailed description in which Fig. 1 is a rear view of oneembodiment of the invention,

Fig. 2 is a sectional View taken along the line 2-2 of Fig. 1,

Fig. 3 is an enlarged view of means for holding the connecting link,

Fig. 4 is a sectional view of Fig. 3 along the line 44.

Similar reference characters designate similar parts in the variousviews.

In Figs. 1 and 2, there is shown a diaphragm comprising a plurality ofsections or panels 20, 21 and 22 of thin material such as metal orfibrous material but preferably of balsa Wood. In practice it has beenfound that balsa Wood panels 6 x 36" x are Well suited. These panels maybe sccuredin a frame 2 with glue. nails, screws or the like. The panelsare slightly separated at their jacent longitudinal edges to avoidrubbing but are sufliciently close to prevent the passage of air whenthe diaphragm is vibrated. A separation of has been found to givesatisfactory results. Angularly disposed bridging members such as 3, 4,5 and 6 extending over adjacent panels are suitably fixed thereto as bygluing. These members may be tapered and are preferably terminated ashort distance from the supports at the edges of the diaphragm so thatthe energy communicated to the diaphragm by the driying means isdissipated before it reaches said supports. A supporting member 7suitably mounted on the frame 2 carries a driving means 8, which may beof any desired type. An example of a suitable type is disclosed inPatent No. 1,365,898 to Edgerton of January 18, 1921.

A member 9, secured to the bridging members such as 3, 4, 5 and 6,carries a hub 10 to which a link or rod 11 connected to the drivingmechanism 8 may be secured by the screw 12.

\Vhere adiaphragm is large, it is apt to warp or bend with temperatureand humidity changes. Furthermore Where Wood is used for the diaphragmit is difiicult to get large panels of uniform structure. It is for thepurpose of overcoming these difficulties met with in practice that thediaphragm is made up of a plurality of panels. Another advantage ofusing a plurality of panels is that the vibration characteristics ofeach of them may be controlled. For example, the thicknesses of thevarious panels may be varied thereby tuning them to any desiredfrequency.

Balsa WOOCl is light, has a high ratio of stiffness to weight, issubstantially homoge" neous in structure and for these reasons it ispreferred.

Although the diaphragm,as illustrated in the drawing is rectangular inform, it will be understood that it ma be of other shape as V forexample square or e iptical.

If desired the front of the diaphragm may be covered with a fabric, suchas tapestry with a suitable design thereon.

It is not desired to limit this invention to the precise details ofconstruction and di-,

mensions herein set forth, as it is obvious that various modificationsmay be made Wltl1- out departing from the essential features of theinvention as defined in the appended claims.

hat is claimed is:

1. A sound reproducing diaphragm comprising a plurality of wooden panelsarranged in a plane with their adjacent edges out of contact butsufficiently close together to provide a large frictional resistance tothe passage of air, whereby said panels act acoustically as a singleimperforate panel.

2. A sound reproducing diaphragm comprisin a plurality of thin panels off brous material arranged in a plane with their adjacent edges separatedto avoid rubbing when vibrating, but sutfieiently close to prevent the fll) passage of an appreciable'amount of air between the panels.

3. A sound reproducing diaphragm comprising a plurality of thin panelsof balsa wood arranged in a plane with their adjacent longitudinal edgesslightly separated and means extending across separated portions of saidpanels for uniting said panels into a unitary structure.

4. A sound reproducing device comprising a plurality of fiat panelsarranged in a plane with their adjacent edges slightlyseparated,angularly disposed members attached to said panels, a frame at the outeredges of said panels, and means for securing the outer edges of saidpanels to said frame.

5. A sound reproducing device comprising a plurality of flat panelsarranged in a plane with adjoining edges suificiently close together tooffer a large frictional resistance to the passage of air, angularlydisposed and radially extending bridging, members for said panels, adriving mechanism and a link connecting said mechanism and the junctionpoint of said bridging members.

6. A sound reproducing device comprising a diaphragm consisting of aplurality ofthin panels of balsa wood arranged adjacent each other withtheir adjoining edges slightly seprated, means for rigidly holding thediaphragm at its outer edges, angularly disposed bridging membersextending to points near the edge of said diaphragm and means attachedto said bridging members for imparting vibrational forces thereto.

7. A sound reproducing device comprising a diaphragm having a pluralityof rectangular shaped panels of balsa wood arranged in a plane, aplurality of light ribs uniting said panels together, means for rigidlyholding said diaphragm at its outer edges, and means for impartingvibrational'forces to said diaphragm. v

8. A sound reproducing device comprising a diaphragm composedof aplurality of wooden panels arranged in a plane with their adjacent edgessufficiently'close together to offer a large frictional resistance tothe passage of air, means extending over a face of said panels unitingthem into a unitary structure, a frame about the edges of saiddiaphragm, and means mounted on said frame for imparting vibrationalforces to said diaphragm.

9. A sound reproducer comprising a plurality of thin strips of balsaWood separated from each other and securely held in a suitable frame, incombination with vibration transmitting means to which vibrations aremeans being securely fastened to each of said strips.

10. A sound reproducer comprising a plurality of thin strips of balsawood separated from each other and securely held in a suit,

combination with common vibration transmitting means securely fastenedto each of said strips, and a source of vibrations securely coupledthereto.

. 12. A sound reproducer having a diaphragm of balsa wood insubstantially its natural state.

13. A diaphragm for sound reproducing devices, comprising a plurality ofstrips or panels rigidly supported in spaced relation to one another,and vibration transmitting means for transmitting vibrations from asuitable source of vibrations to said strips or panels, said means beingsecured to said strips or panels and tying them together in a unitarystructure.

14. A sound reproducer having in combination, a diaphragm comprising aplurality of thin strips of balsa wood separated from each other, aframe, means for securing said thin strips of balsa wood in the frame,vibration transmitting means securely fastened to each of said strips, asource of vibrations and a connection between said source and thediaphragm to produce "vibrations of the diaphragm.

15. A sound reproducer having in combination a diaphragm comprising aplurality of thin strips of balsa wood separated from each other, aframe, means for securing said strips in said frame, vibrationtransmitting means securely fastened to each of said strips, saidvibration transmitting means including a plurality of fins crossing saidstrips and arranged in engagement therewith, a source of vibrations. anda connection between said source and the diaphragm to produce vibrationsof the diaphragm.

In witness whereof, I hereunto subscribe myTname this 16th day ofFebruary, A. 1)., 192

JAMES L. cnoucn.

